Secondary batteries which are highly applicable to various products and exhibit superior electrical properties such as high energy density, etc. are commonly used not only in portable devices but also in electric vehicles (EVs) or hybrid electric vehicles (HEVs) driven by electrical power sources. The secondary battery is drawing attentions as a new energy source for enhancing energy efficiency and environment friendliness in that the use of fossil fuels can be reduced greatly and no byproduct is generated during energy consumption.
Secondary batteries widely used at the preset include lithium ion batteries, lithium polymer batteries, nickel cadmium batteries, nickel hydrogen batteries, nickel zinc batteries and the like. An operating voltage of the unit secondary battery cell, namely a unit battery cell, is about 2.5V to 4.2V. Therefore, if a higher output voltage is required, a plurality of battery cells may be connected in series to configure a battery pack. In addition, depending on the charge/discharge capacity required for the battery pack, a plurality of battery cells may be connected in parallel to configure a battery pack. Thus, the number of battery cells included in the battery pack may be variously set according to the required output voltage or the demanded charge/discharge capacity.
Meanwhile, when a plurality of battery cells are connected in series or in parallel to configure a battery pack, it is common to configure a battery module composed of at least one battery cell first, and then configure a battery pack by using at least one battery module and adding other components.
The conventional battery packs generally include at least one battery module and a pack case for packaging the at least one battery module. Here, the pack case is generally made of a metal material such as steel for ensuring rigidity and shielding electromagnetic noise. In addition, an outer surface of the pack case is coated with a nonconductive material such as epoxy for protecting the exterior and preventing corrosion.
However, in the conventional battery pack, since the pack case for packaging the battery module is made of a metal material, when the battery module is ignited due to a fire or overheating of the battery module in the battery pack, a fire extinguishing liquid sprayed from an extinguishing device such as a fire extinguisher to extinguish the ignition may not easily flow into the pack case.
Accordingly, in the conventional battery pack, it is difficult for the fire extinguishing liquid to flow smoothly into the battery module inside the pack case when a fire or overheating occurs at the battery module in the pack case, and thus there is a greater risk of secondary damages, such as an explosion of the battery pack due to the expansion of the battery module or a chain explosion of a vehicle or the like to which the battery pack is mounted.
Therefore, it is requested to find a way to allow a fire extinguishing liquid for fire suppression to smoothly flow into the pack case when a fire or overheating occurs at the battery pack.